Such a device is described in EP 0 219 570 B1 or U.S. Pat. No. 4,713,498. It replaces simpler versions which can only be used for one method of mounting. Two mounting methods are made possible by the fact that clamping screws of connection terminals are rendered accessible from different sides. Typical mounting methods would be fixing an electrical device on to a mounting rail by its rear surface, for example inside a control board, or mounting on the rear of a control panel by its front surface. As the same device can be used for various applications the result is lower stock-holding and transport costs.
In order to adapt it to different mounting methods the prior art electrical device has terminals whose clamping screws for the connection contacts are located in separable connection blocks which one can chose to fix in one of two opposed positions on the side walls of the electrical device enclosure, so that the same clamping screws are accessible either from the front or the back of the enclosure. In this case the electrical device and the separable connection blocks have first of all to be assembled in the necessary position corresponding to the type of mounting, before installation. This demands extra time. In addition the manufacturer cannot absolutely guarantee a correct mounting of the connection blocks. If the mounting is incorrectly carried out or if the connection blocks are accidentally forgotten serious dangers can arise since the unprotected electrical connection contacts may be energized after the device has been partially wired up and accidents can be caused by human contact.